Many hose constructions exist in the prior art which may be used in high pressure applications. Such hose constructions generally fall into four general types. The first type is a simple hose construction consisting of a liner of an elastomeric material with a braided cover of fiber or metal. Such a hose construction has a large bend radius and kinks when bending. It has poor flexibility and both balloons and elongates under pressure. No adhesion is provided between the cover and liner and problems arise in fitting ends thereon due to cold-flow or compression set. Such hoses are thus generally limited to low pressure applications, have a short flexibility life and do not withstand negative pressures.
In order to minimize these problems, a second type of hose construction is known wherein the inner liner is convoluted or corrugated, the remainder of the hose construction being identical to the first type heretofore described. This second type of hose construction has a medium bend radius and restricted flow due to the configuration of the inner liner. Such convolutions or corrugations create flow turbulence and such hoses kink when bent beyond their bend radii. There is still no adhesion between the cover and the liner and the liner has a thin wall at the top of the convolutes or corrugations thus resulting in possible leakage. Such hoses also balloon and extend under pressure and, due to the liner configuration, create problems when fitting ends thereto. Finally, this second type of hose construction does not withstand negative pressures.
A third type of hose construction has been proposed to overcome or minimize the problems of the aforementioned first and second types of hose constructions. This third type of hose construction consists of a multiple reinforced hose to achieve high pressure rating and improved bend characteristics. The first ply is the liner which is of a smooth extruded elastomeric material, such as an elastomer or thermoplastic material. This liner is covered by a second ply of a braided fiber or wire material. A third ply covers the braided ply and is a thin elastomeric tie ply, such as an elastomer or thermoplastic material, which promotes adhesion between the second and fourth ply. This fourth ply is identical to the second braided ply. Finally, the entire hose is covered by a fifth ply of extruded tubular material compatible to the first or liner ply.
Although this third type of hose construction has advantages over the aforementioned first two types, it requires a thick wall due to the multiple ply lay-up and is thus heavy in weight, must be manufactured in several stages, is expensive to manufacture, has a limited bend radius, and is costly due to the materials used to make it.
Finally, a fourth type of hose construction has been suggested which is of a helical wire reinforced tube design. Such a hose has an inner liner of either sheet material or a coated fabric type. A wire helix is formed over the liner or cover at a predetermined pitch (i.e., the distance between the flytes of the wire helix). This helix is covered with a material compatible with the liner and a pre-coated cord is placed between the wire flytes. The pitch distance regulates the bend radius of the hose and the wire and cord arrangement improves the pressure rating. It is also heavy in weight and still has a relatively low pressure rating. It requires a hand lay-up process to manufacture and the materials used are expensive. Such a hose cannot crimp onto end fittings and must be manufactured in short lengths in a semi-automatic manufacturing process.